The present invention relates to a magnetic tape recording apparatus having a plurality of rotary magnetic heads in which a newly designed flying erase head is provided so that only a necessary region on the magnetic tape can suitably be erased when the tape is moved to record information signals thereon in the forward direction and in the reverse direction.
FIG. 1 shows a tape format of a so-called 8 mm video tape recorder.
In FIG. 1, numeral 2 denotes a magnetic tape, numeral 3 denotes a recording track, numeral 4F denotes a tape moving direction during normal recording and 4H denotes a head scanning direction.
A length of each recording track 3 corresponds to a rotation angle of 216.degree. of a rotary magnetic head. An audio signal is usually recorded on a segment 3S of each track 3 (denoted by hatched the area of each track in FIG. 1) corresponding to a rotation angle of 36 degrees of the rotary magnetic head and, on the other hand, a video signal is usually recorded on the remaining segment 3V of each track 3 (denoted by blank the area of each track in FIG. 1) corresponding to an angle of 180.degree. of the rotary magnetic head. It should be noted that the audio signal to be recorded on the segment 3S has been converted into a PCM (Pulse Code Modulated) signal and has been compressed to a time axis compressed signal so as to be positioned on the segment 3S. On the other hand, the video signal on the remaining segment 3V is a signal for each field interval, wherein a luminance signal (Y signal) is converted into an FM (Frequency Modulated) signal and a chrominance signal is frequency converted into a lower frequency range. In this case, an odd field chrominance signal and an even field chrominance signal are modified to have a frequency-interleaving relationship with each other.
Furthermore, one track is located adjacent to another track and one azimuth angle with respect to each record pattern on one group of tracks grouped for every other track and the other azimuth angle with respect to each record pattern on the other group of remaining tracks grouped for every other track are different from each other. It should be noted that pilot signals for a tracking servo used during a signal reproducing operation is, furthermore, superposed over the whole length of each track 3.
It should be noted that for simplification of this specification, the length of the audio signal recording segment 3S has been set so as to correspond to the rotation angle of 36 degrees as described above and over the whole length of which the PCM audio signal is recorded.
FIG. 2 shows a conventional arrangement of rotary magnetic heads in the 8 mm video tape recorder.
In FIG. 2, numerals 1A and 1B denote a pair of rotary magnetic heads mounted on a rotary drum 5, having a mutual angular interval of 180 degrees with respect to a center of the rotary drum 5, and rotated in the head scanning direction 4H at a frame frequency (30 Hz) of the video signal. In addition, a rotary erase head 1F is installed at a position on the drum 5 having a different height from the heads 1A and 1B and which corresponds to, e.g., 90 degrees apart from the head 1A, i.e., 90 degrees prior to the head 1A. A track width (erasing i.e. the gap width) of the rotary erase head 1F is twice as wide as each of effective gap widths of the pair of heads 1A and 1B.
The tape 2 is wound spirally over an angular range of 216 degrees or greater on a peripheral surface of the rotary drum 5 and is moved along a predetermined direction denoted by the numeral 4F.
With a flow of erase current into the rotary erase head 1F during the recording operation, one scanning of the head 1F permits a simultaneous erasing of recording patterns on two tracks and thereafter the track 3 is sequentially formed on the tape as shown in FIG. 1 by means of the heads 1A, 1B.
It has been proposed that for the tape format described above, another audio signal is recorded on the video signal recording segment 3V in place of the video signal. FIG. 3 thus shows a multi-audio tape format of the 8 mm video tape recorder.
As shown in FIG. 3, the video recording segment 3V is divided into five segments for each rotation angle of 36 degrees so that each track 3 is divided into six segments along the length thereof. During a first recording of the audio signal, only the segment denoted by (1) among the divided segments (1) through (6) is used when the audio signal is recorded on each track 3. During the second recording thereof, only the segment denoted by (2) among the divided segments (1) through (6) is used when the audio signal is recorded on each track 3. In this way, when the audio signal is recorded, only one of the six divided segments (1) through (6) is selectively used.
It should be noted that, at this time, the audio signal is recorded in the same signal format as the PCM audio signal which is to be recorded on the segment 3S. In addition, an order in which the divided segments (1) through (6) are to be used is arbitrary. Furthermore, while the audio signal on any one of the divided segments (1) through (6) is recorded, the moving direction of the tape 2 is not limited. For example, when the audio signal is recorded on any one of the segments (1), (3) and (5), the tape 2 may be moved in the forward direction 4F and when it is recorded on any one of the segments (2), (4) and (6), the tape 2 may be moved in the reverse direction 4R.
Therefore, the same tape 2 may aribitrarily be used for either video or all audio recording/reproducing medium. If the tape 2 is used for the all audio recording medium, an audio signal recording having an elapsed time six times longer than the video signal recording can be achieved.
Furthermore, since the tape running direction for each of the segments (1) through (6) is not limited, it is not necessary to rewind the tape from a tape end to a tape top when the recording tape has reached the tape end and the tape recording apparatus can conveniently be used as a reversible tape recorder merely by switching the running direction of the tape 2.
The tape recording apparatus described with reference to FIGS. 1 through 3 is exemplified by Japanese Patent Application Serial No. Sho. 57-15,287 filed on Feb. 2, 1982 (published on Dec. 24, 1983 as the Unexamined Open No. Sho 58-222,402 and which corresponds to U.S. patent application Ser. No. 463,337 now pending).
In the above-described all-audio mode of the tape recording apparatus, when the tape 2 is moved in the forward direction to record the audio signal on the segments (1) through (6), the rotary erase head 1F needs to erase a part of the tape surface to be recorded prior to the recording of the audio signal thereon in the same way as the video signal recording operation.
However, when the tape 2 is moved in the reverse direction to record the audio signal on the segments (1) through (6), a part of the tape surface on which either of the heads 1A, 1B has scanned and recorded the audio signal also needs to be scanned by means of the rotary erase head 1F following the scanning operation of either one of the heads 1A, 1B, so that the head 1F immediately erases the already recorded surface on the tape which has been scanned and recorded by either head 1A or 1B. In this case, since the scanning operation of the erase head 1F is followed by the recording operation of either of the heads 1A, 1B, the head 1F always erases any recording segment track part on which either of the heads 1A, 1B carries out the new recording of and audio signal immediately after the new recording operation by means of the head 1A, 1B. Therefore, in the above-described tape recording apparatus, no normal recording of the audio signal on the tape can be made when the tape 2 is moved in the reverse direction.